OXYGEN CONTENT SENSOR INPUT DEVICE

An oxygen concentration sensor input device (1) includes a sensor input circuit (4) that can freely supplies a flow-out current to an oxygen concentration sensor (2) that detects an oxygen concentration in exhaust gas of an internal combustion engine. The sensor input circuit includes an operational amplifier (12) that constitutes a voltage follower. A current value of the flow-out current is set such that a voltage waveform of a detection signal of the oxygen concentration sensor crosses a detection threshold on a low voltage side.